China
Africa
Explore chapters and articles related to this topic
Personal Protective Equipment (PPE): Practical and Theoretical Considerations
Published in Brian J. Lukey, James A. Romano, Salem Harry, Chemical Warfare Agents, 2019
Activated carbon (AC) (sometimes referred to as activated charcoal) is a specially formulated carbon-based product. It is principally used to adsorb organic compounds and pollutants from liquid and gas streams. Although organic chemical compounds are attracted best to carbon, carbon has little affinity for removing inorganic chemicals. Examples of organic chemicals removed by AC include benzene, toluene, xylene, oils, and some chlorinated compounds as well as odor and color contamination. Factors affecting its capability in removing chemicals include, but are not limited to, molecular weight, solubility in water, polarity, and temperature of the fluid stream (General Carbon, 2016b). Additionally, AC may serve as a catalyst (which promotes or speeds up a chemical reaction but at the end of the chemical reaction, is not itself changed), since its active surface provides a far greater distribution of catalytically active atoms than are available on the corresponding metal (Shabanzadeh, 2012). In the United States in 2002, approximately 200,000 tons were produced (Jabit, 2007).
Health and water chemistry
Published in Sandy Cairncross, Richard Feachem, Environmental Health Engineering in the Tropics, 2018
Sandy Cairncross, Richard Feachem
Some other organic chemicals are known to cause cancer when consumed in large doses and to occur in minute concentrations in drinking water supplies. In the USA the use of granular activated carbon treatment is recommended to reduce organic compounds in public drinking water supplies. Particular attention has been paid to polynuclear aromatic hydrocarbons (PAHs) and to trihalomethanes (THMs). The WHO (2011) Guidelines for Drinking-water Quality for carcinogens are set on the basis of an estimated risk of one case of cancer per 100,000 people in a 70-year lifetime. On this basis, they recommend that the concentration of one representative PAH in drinking water (benzo[a]pyrene) should not exceed 0.7 μg/l, although water normally contributes a small minority of people’s total PAH intake. The occurrence of benzo[a]pyrene in drinking water is usually associated with the use of coal-tar linings in iron pipes and in reservoirs; WHO recommends that their use be discontinued, but not that the affected pipes be replaced. As with pesticides, central and sophisticated laboratory facilities are required to detect and identify these chemicals in drinking water.
What is iodine?
Published in Tatsuo Kaiho, Iodine Made Simple, 2017
In the copper method, a reaction is created by placing cuprous sulfate and ferrous sulfate in a brine. Copper iodide is allowed to precipitate, then any sediment is filtered and washed out in order to obtain crude copper iodide with approximately 50% iodine concentration. Next, after drying, the crude copper iodide is heated and oxidative decomposition is carried out to obtain iodine. In the activated carbon absorption method, sulfuric acid is added to the brine and after adjusting pH value to 2–4, sodium nitrite is added as an oxidant to liberate the iodine. Activated carbon, at approximately 7 times the quantity of free iodine, is added to absorb the iodine. Next, sodium hydroxide and sodium carbonate are added to the activated carbon with the absorbed iodine and heated, which is subsequently eluted as sodium iodide. This solution is concentrated in an iron pot, then acidified by sulfuric acid and oxidized with chlorine, resulting in the precipitation of iodine.
First report on the presence of aflatoxins in fig seed oil and the efficacy of adsorbents in reducing aflatoxin levels in aqueous and oily media
Published in Toxin Reviews, 2022
The effects of various adsorbent treatments on some physicochemical characteristics of fig seed oil are given in Table S2. The absorbance values of fig seed oil at 435.5 and 459.5 nm were 0.81 ± 0.01 and 0.72 ± 0.01, respectively, before adsorbent treatments. It was determined that, in general, the adsorbent treatments did not have any significant effect on the absorbance values of the fig seed oil. The only exception to this situation was the result obtained with activated carbon treatment. Treating the fig seed oil with activated carbon at a concentration of 0.1% resulted in 20.9% and 22.2% reductions in the absorbance values at 459.5 and 435.5 nm, respectively. These rates were recorded as 32.1% and 22.2% after treating with activated carbon concentration of 5.0%. This result shows that activated carbon could adsorb the compounds such as chlorophylls and carotenoids that contribute to the color of the fig seed oil. Similarly, decreases in the color values of fish oil (Monte et al. 2015) and soybean oil (Udomkun et al. 2018) were observed after activated carbon treatments.
Correlations between pore textures of activated carbons and Langmuir constants – case studies on methylene blue and congo red adsorption
Published in Toxin Reviews, 2022
Fadina Amran, Muhammad Abbas Ahmad Zaini
Activated carbon is produced through physical or chemical activation. Chemical activation has been widely applied in research works because it offers lower activation temperature and time, and higher carbon yield and surface area. Chemical agents such as phosphoric acid (Benadjemia et al.2011, Nahil and Williams 2012), potassium hydroxide (Seo et al.2019, Bhomick et al.2019), zinc chloride (Anisuzzaman et al.2018, Laverde et al.2019), calcium carbonate (Garba et al.2015, Li et al.2018) and sodium hydroxide (Liew et al.2019, Guo et al.2020) have been investigated in chemical activation of activated carbon. Hasanzadeh et al. (2020) reported a high surface area of 2760 m2/g by potassium hydroxide activation of date press cake that yields a 572 mg/g removal capacity of cefixime. Also, the surface area for activated carbon by zinc chloride activation is higher at 1374 m2/g as compared to 206 m2/g of its sunflower seed hull char (Vunain et al.2018).
Dyes adsorption properties of KOH-activated resorcinol-formaldehyde carbon gels -kinetic, isotherm and dynamic studies
Published in Toxin Reviews, 2022
Azrul Nurfaiz Mohd Faizal, Muhammad Abbas Ahmad Zaini
A 0.05 g of activated carbon was added into Beatson bottles containing 50 ml of methylene blue (MB) or congo red (CR) dyes of varying concentrations (5 to 300 mg/L) (Hui and Zaini 2015). The bottles were sealed and the mixtures were allowed to equilibrate for 20 days. The residual concentration was measured using a UV-vis spectrophotometer (Spectrumlab 752 Pro) at wavelengths of 620 nm for MB and 488 nm for CR. The capacity at equilibrium, qe (mg/g) was calculated by simple mass balance, Co and Ce (mg/L) are initial and equilibrium concentrations, respectively, V (L) is the volume of the solution and m (g) is the mass of dry adsorbent. The equilibrium data were analyzed using four isotherm models, i.e., Dubinin-Radushkevich, Freundlich, Langmuir and Redlich-Peterson. Similar settings were replicated for adsorption kinetic. A 0.05 g of activated carbon was added to different batches of 50 ml of dye solutions at concentrations of 5 mg/L, 10 mg/L and 20 mg/L (Zaini et al.2017). The residual concentration was measured at preset time intervals for 8 days. The kinetics data were analyzed using intraparticle diffusion, pseudo-first-order, pseudo-second-order and Boyd’s models.